Background. The Occluded Artery Trial (OAT) is an international randomized trial of 3200 patients, funded by the NHLBI in order to determine if delayed mechanical reperfusion by means of percutaneous transluminal coronary angioplasty (PTCA) and stenting reduces the important composite clinical endpoint of death, MI, and hospitalization for NYHA Class IV heart failure in patients with a persistently occluded infarct-related artery (IRA) 3-28 days after myocardial infarction (MI). While left ventricular (LV) function improvement has been suggested as one mechanism behind a postulated benefit of late reperfusion, solid evidence is lacking. Furthermore, while stenting has reduced reocclusion rates after total occlusion PTCA, the reocclusion rate after a recent MI is unknown. In reviewing the OAT grant application, NHLBI reviewers specifically raised a concern regarding a need to track long-term patency in the study population. The TOSCA-2 substudy addresses this concern directly. Hypothesis The central hypothesis of the TOSCA-2 angiographic patency that will improve LV function in patients with an occluded IRA after a recent (3 - 28 days) MI. Specific aims. TOSCA-2 is a 380 patient mechanistic substudy of OAT with 2 primary specific aims: 1) to compare long-term patency rates between the 2 treatment groups by means of follow-up coronary angiography 1year after randomization, and 2) to compare the change in global LV ejection fraction between the 2 treatment groups utilizing baseline and follow-up contrast LV angiograms. Secondary aims include: 1) comparison of regional wall motion and LV volumes, 2) study of the effect of reocclusion and spontaneous recanalization on LV function,, and 3) to study the effect of duration of occlusion on changes in LV function after PCI in this setting. Operations. The substudv will be conducted in 21 OAT participating centers. The Substudy Coordinating Center (SCC) is at the University of Alberta in Edmonton, Canada. The Substudy Chair is a member of the OAT Executive Committee and reports directly to the Study Chair and Ancillary Studies Committee of OAT. The Data Coordinating Center (DCC) is the Maryland Medical Research Institute, the DCC of OAT. The An2iogiraphic Core Laboratory is at the University of British Columbia.